1. Field of the Invention
The present invention relates to a plunger lock mechanism, and more particularly, to a plunger lock mechanism of the type which is useful in securing a sliding door of a cabinet or the like in its closed position.
2. Description of the Prior Art
Plunger lock mechanisms are normally operable by means of a key and include elements which are axially reciprocable between a locked position and an unlocked position; that is, they are reciprocable in opposite directions corresponding to the directions of key insertion and removal. Those plunger lock mechanisms which incorporate a conventional rotatable plug lock are reciprocable along the axis of rotation of the plug lock.
An example of such a mechanism is disclosed in U.S. Pat. No. 4,009,599, issued Mar. 1, 1977, to G. P. Patriquin, and comprises a shell reciprocable in a housing between a locked position and an unlocked position in response to operation by a key. A locking slot is provided by an aperture in the housing, and a locking wafer or bolt carried by the shell and movable radially relative thereto is releasably received in the locking slot, whereby to maintain the shell in the locked position. The wafer is biased toward its radially outer position; that is, toward its locking position, by a spring. It is retracted to its radially inner position, whereby to permit the shell to be moved to its unlocked position, by means of a stud received in a particularly configured cam opening formed centrally of the locking wafer. The stud extends axially from a conventional plug lock carried by the shell and is therefore moved in a circular path as the plug lock is rotated by means of the key. The stud, acting on the cam edge which defines the central opening of the locking wafer, operates to retract the wafer to its unlocking position. Specific reference is made to sliding door locks.
Such locks are highly subject to wear at the engaging surfaces of the stud and the cam edge of the wafer opening. Eventually, this wear may cause failure of the lock mechanism, because movement of the stud will no longer cause the locking wafer to be fully retracted from the locking slot in the housing. Also, the stud may be subjected to excessive shearing forces exerted by the cam edge if undue force is applied to the locking mechanism or the key.
Another lock of the plunger type is disclosed in U.S. Pat. No. 3,345,838, issued Oct. 10, 1967 to F. J. Russell et al. Here, a lock plunger or cylinder assembly is axially slidable within a lock case. A lock bolt extends outwardly of the lock plunger and through an opening in the lock case to be disposed in an interfering position relative to a sliding door when the lock plunger is in its innermost position in the lock case. Axial movement of the lock plunger outwardly relative to the lock case causes the lock bolt to be moved out of its interfering position relative to the sliding door. A latch pawl, controlled by a key received in a key plug mounted in the lock plunger, engages a detent provided in the wall of the lock case. The detent is formed with a sloping surface which acts to cam the latch pawl inwardly as the lock plunger is urged into the lock case to a locking position. Means contained entirely within the lock plunger act, upon rotation of the key in the key plug, to cause the latch pawl to be retracted so that the lock plunger can be withdrawn to the unlocked position. Included in the means contained within the lock plunger is a pivot pin subject to wear and shearing forces in the manner of Patriquin's stud, above.